1. Field of the Invention
This invention relates to a semiconductor device which permits easy reduction in interwiring capacitance and also to a method for manufacturing same.
2. Description of the Related Art
In the damascene structure of copper (Cu) wiring, as shown in FIG. 20, a barrier film 213 is formed on the inner surfaces of a wiring recess 212 formed in an oxide film 211 for the purpose of preventing copper from diffusing into the oxide film 211. In general, for the barrier film 213 formed at side walls and a bottom portion of the wiring recess 212, there are frequently used metal materials such as tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN), tungsten nitride (WN) and the like, and for an insulating film 215 on the upper surface of a copper wiring 214 formed inside the wiring recess 212 through the barrier film 213, silicon insulating film materials are frequently used including materials for chemical vapor deposition such as, for example, silicon nitride (SiN), silicon nitride carbide (SiCN), silicon carbide (SiC), SiCON and the like.
The properties necessary as the barrier film 215 formed on the upper surface of the copper wiring 214 include, aside from the barrier property for suppressing diffusion of copper, a dielectric constant of the barrier film 215 itself, adhesion between the barrier film and interfaces thereof, and processing flexibility of the barrier film 215, which are considered as important parameters for robust process establishment. Especially, with a 65 nm generation and subsequent devices, an influence on working speeds of circuits is occupied largely by wiring units. The barrier film on the upper surface of the copper wiring 214 is required to have such characteristics as mentioned above while lowering the dielectric constant.
For the barrier insulating film suppressing copper diffusion, a difficulty is involved in satisfying such characteristics as mentioned above (e.g. a barrier property for suppressing copper diffusion, adhesion between the barrier film and interfaces thereof, film stress, and processing flexibility and the like) while satisfying a requirement for dielectric constant of 65 nm generation and subsequent devices. An instance of the relationship between the dielectric constant of a barrier insulating film and various characteristics has been introduced in literature (e.g. Z. C. Wu, T. J. Chou, S. H. Lin, Y. L. Huang, C. H. Lin, L. P. Li, B. T. Chen, Y. C. Lu, C. C. Chiang, M. C. Chen, W. Chang, S. M. Jang, and M. S. Liang, “High Performance 90/65 nm BEOL Technology with CVD Porous Low-K Dielectrics (K˜2.5) and Low-K Etching Stop (K˜3.0)” International Electron Device Meeting Tech. Dig., December 2003, p. 849-852, 2003), and the dielectric constant and various characteristics of the barrier insulating film are in trade-off relation.
A technique of forming a barrier insulating film for copper by so-called self-forming is known using a copper-manganese (CuMn) alloy seed layer as a barrier insulating film for copper (see, for example, T. Usui, H. Nasu, J. Koike, M. Wada, S. Takahashi, N. Shimizu, T. Nishikawa, M. Yoshimura and H. Shibata, “Low resistive and Highly Reliable Cu Dual-Damascene Interconnect Technology Using Self-Formed MnSixOy Barrier Layer”, International Interconnect Technology Conference 2005, p. 188-190, 2005).